A large static magnetic field is used by Magnetic Resonance Imaging (MRI) scanners to align the nuclear spins of atoms as part of the procedure for producing images within the body of a patient. This large static magnetic field is referred to as the B0 field.
During an MRI scan, Radio Frequency (RF) pulses generated by a transmitter coil cause perturbations to the local magnetic field, and RF signals emitted by the nuclear spins are detected by a receiver coil. These RF signals are used to construct the MRI images. These coils can also be referred to as antennas. Further, the transmitter and receiver coils can also be integrated into a single transceiver coil that performs both functions. It is understood that the use of the term transceiver coil also refers to systems where separate transmitter and receiver coils are used. The transmitted RF field is referred to as the B1 field.
During longer scan the subject can have internal or eternal motion which corrupts the data and results in images with blurs or artifacts. One way of countering this is by acquiring the magnetic resonance imaging data in groups and then correcting the magnetic resonance data to account for motion of the subject. In the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) the magnetic resonance imaging data is acquired in rectlinear blocks referred to as blades. The blades are rotated with respect to each other in k-space and have an overlapping region in the center of k-space. A comparison of the overlapping region for the different blades enables compensation for motion of the subject. The PROPELLER protocol is for example reviewed on pages 915 to pages 919 of “the handbook of MRI Pulse Sequences” by Bernstein et al. published by Elsevier Academic Press, 2004.
In parallel imaging techniques multiple antenna elements are used to acquire data simultaneously. A coil sensitivity matrix or coil sensitivity maps (CSM) contains a spatial sensitivity of each of the antenna elements. The coil sensitivity maps are then used to combine the data acquired using each of the individual antenna elements into a single composite image. This greatly accelerates the acquisition of the magnetic resonance image. Magnetic resonance parallel-imaging reconstruction techniques are briefly outlined in section 13.3 of Bernstein et. al.
U.S. Pat. No. 7,102,348 B2 discloses a method of performing a PROPELLER magnetic resonance imaging protocol combined with a partial acquisition technique.
The doctoral dissertation “Improvements to highly accelerated Parallel Magnetic Resonance Imaging” by Richard Winklemann, Fakultät für Elektrotehcnik and Informationstechnik der Universitat Fridericiana Karlsruhe, 2006 discloses several methods of removing ghosting artifacts and image folding artifacts for SENSE reconstructed magnetic resonance images using a least squares (Chi squared) fit deviation.
The US-patent application US2006/0232273 concerns a PROPELLER acquisition in which under sampling in k-space is used. Aliasing images are reconstructed per blade and on the basis of the coil sensitivity distribution data, unfolded images for respective blades are formed.